Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Journal of Natural History, 2001, 35, no. 12, 1733–1772 Trematodes of the family Heterophyidae (Digenea) in Mexico: a review of species and new host and geographical records T. SCHOLZ*²³, M. L. AGUIRRE-MACEDO² and G. SALGADO-MALDONADO§ ² Centre for Investigation and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN) Unidad MeÂrida, Carretera Antigua a Progreso Km 6, A.P. 73 `Cordemex’, C.P. 97310 MeÂrida, YucataÂn, Mexico; e-mail: leo@kin.cieamer.conacyt.m x ³ Institute of Parasitology, Academy of Sciences of the Czech Republic, BranisÆovska 31, 370 05 CÏeske BudeÏjovice, Czech Republic; e-mail: tscholz@paru.cas.c z § Institute of Biology, National Autonomous University of Mexico (UNAM), A.P. 53-173, C.P. 04510 MeÂxico, D.F., Mexico; e-mail: gsalgado@ibiologia.unam.m x (Accepted 26 May 2000) A review of heterophyid trematodes found in Mexico, both as metacercariae encysted in ®sh and adults in ®sh-eating birds and mammals, is presented, including numerous new geographical and host records. Data on the morphology, spectrum of intermediate and de®nitive hosts, site of infection of metacercariae, distribution in Mexico and biology of the following species are provided (species ®rst reported from Mexico marked with an asterisk): *Ascocotyle (Ascocotyle) gemina Font, Overstreet and Heard, 1984; A. (A.) leighi Burton, 1956; A. (A.) tenuicollis Price, 1935; A. (Leighia) chandleri Lumsden, 1963; *A. (L .) mcintoshi Price, 1936; A. (L .) megalocephala Price, 1932; A. (L .) nunezae Scholz, VargasVaÂzquez, Vidal-MartõÂnez and Aguirre-Macedo, 1997; Ascocotyle (Leighia) sp.; *A. (Phagicola) ampullacea Miller and Harkema, 1962; A. (P.) diminuta Stunkard and Haviland, 1924; A. (P.) macrostoma (Robinson, 1956); *A. (P.) longa Ransom, 1920; A. (P.) nana Ransom, 1920; Centrocestus formosanus (Nishigori, 1924); *Euhaplorchis californiensis Martin, 1950; Galactosomum puni Yamaguti, 1941; *Haplorchis pumilio (Looss, 1896); Heterophyidae gen. sp. ( 5 Haplorchoides sp. of Scholz and Vargas-VaÂzquez, 1998); *Phocitremoides ovale Martin, 1950; and *Pygidiopsis pindoramensis (Travassos, 1929). Two of the above-listed species, C. formosanus and H. pumilio, have been introduced recently to Mexico, most probably from Asia with the imported thiarid snail Melanoides tuberculata (MuÈller). Metacercariae of heterophyid trematodes are among the most frequent and abundant parasites of ®sh in Mexico, in particular in its southeastern part. Keywords: Heterophyidae, ®sh, Mexico, taxonomy, biology, geographical distribution. *To whom correspondence should be addressed. Journal of Natural History ISSN 0022-293 3 print/ISSN 1464-526 2 online Ñ 2001 Taylor & Francis Ltd http://www.tandf.co.uk/journals Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1734 T. Scholz et al. Introduction Trematodes of the family Heterophyidae are frequent intestinal parasites of ®sheating birds (SepuÂlveda et al., 1994, 1996, 1999) and their metacercariae encyst in diŒerent organs of ®sh ( Yamaguti, 1971, 1975). In Mexico, metacercariae of heterophyids represent one of the dominant groups of trematodes parasitizing ®sh ( AguirreMacedo and GarcõÂa-MaganÄa, 1994; Scholz et al., 1995, 1997a; Salgado-Maldonad o et al., 1997; Scholz and Vargas-VaÂzquez, 1998; Scholz and Aguirre-Macedo, 2000). Despite this fact, little attention has been paid to these trematodes, most probably because of their small size and dicult taxonomy. Scholz et al. ( 1997a) revised species of the Ascocotyle-complex and provided descriptions of metacercariae from ®sh and adults from naturally and experimentally infected hosts, and a key to identi®cation of metacercariae from the YucataÂn Peninsula. Data on the life cycles of heterophyids in Mexico are very scarce and cercariae of only a limited number of species are known (Ditrich et al., 1997; Scholz et al., 1997a, 2000). Recent investigations into the helminth parasites in Mexico have revealed the presence of numerous trematodes of the family Heterophyidae, many of them previously not reported from this country. Considering the number of taxa recorded from Mexico for the ®rst time, numerous new data on species previously reported and a shortage of the information about heterophyids in Latin America in general, the species of the family Heterophyidae found in Mexico are reviewed and data on their morphology, intermediate and de®nitive hosts, the site of infection in ®sh, geographical distribution and biology are provided. Materials and methods The present survey is based mainly on examination of numerous specimens of heterophyid trematodes collected recently by the present authors in diŒerent parts of Mexico (see Survey of species for individual localities), and on previously published data, in particular those of the present authors (Salgado-Maldonad o and Aguirre-Macedo, 1991; Aguirre-Macedo and GarcõÂa-MaganÄa, 1994; Scholz et al., 1995, 1997a, 1997b; Salgado-Maldonad o et al., 1997; Scholz and Vargas-VaÂzquez, 1998; Scholz, 1999). Localities from where cichlid ®sh were collected are described by Vidal-MartõÂnez et al. (2000 ). Most metacercariae from ®sh were observed in vivo; some were isolated from cysts using preparation needles and ®xed with glycerin:picric acid ( Ergens, 1969). Adult trematodes from naturally and experimentally infected hosts (the great blue egretÐArdea herodias Linnaeus, and chicks, ducks and mice, respectively) were ®xed with hot 4% formaldehyde solution (see Scholz and Aguirre-Macedo, 2000) and stained with hydrochloric carmine (see Scholz and HanzelovaÂ, 1998). Internal morphology, including the structure of the terminal genitalia and the number of circumoral spines, was observed using Nomarski interference contrast. In addition to the types and vouchers studied previously by the present authors (see Scholz et al., 1997a, 1997b), the paratypes of Ascocotyle (A.) chandleri and A. (L .) ampullacea, deposited in the US National Parasite Collection, Beltsville, MD, USA ( USNPC 59584 and 59894, respectively) , were examined. Reference specimens are deposited in the Natural History Museum, London, UK (BMNH ); helminthological collection of the Laboratory of Parasitology, CINVESTAV-IPN MeÂrida (CHCM ); National Helminthological Collection of Mexico, Institute of Biology, UNAM, Mexico City (CNHE ); helminthological collection of the Institute of Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1735 Parasitology, Academy of Sciences of the Czech Republic, CÏeske BudeÏjovice ( IPCAS ); and US National Parasite Collection, Beltsville, MD, USA ( USNPC ). Species reported from Mexico for the ®rst time are marked with an asterisk. All measurements given in descriptions are in micrometres ( mm). Species of the Ascocotyle-complex are considered to belong to the genus Ascocotyle Looss, 1899 sensu lato, i.e. as de®ned by Sogandares-Berna l and Lumsden (1963). Subgeneric classi®cation used in the present paper also follows that proposed by SogandaresBernal and Lumsden (1963), i.e. subgenera Ascocotyle Looss, 1899; Phagicola Faust, 1920; and Leighia Sogandares-Berna l and Lumsden, 1963, with some modi®cations. The systematics of the oviparous killi®sh (Cyprinodontidae) follows that presented in an unpublished annotated checklist by Dr Kenneth J. Lazara, American Museum of Natural History, New York (personal communication) . Survey of species *Ascocotyle (Ascocotyle) gemina Font, Overstreet and Heard, 1984 (®gure 1A±D) Metacercaria Morphology. (Morphology based on seven ¯attened specimens from Garmanella pulchra Hubbs.) Cyst oval, with relatively thick external and thin, membraneous internal walls, 294 long and 250 wide. Body elongate, 470±680 long and 140±170 wide, slightly tapering anteriorly but with wide anterior end, covered with tegumental spines decreasing in size posteriorly. Tegumental spines simple-pointed, long and slender. Remnants of eye-spots scattered between pharynx and intestinal bifurcation. Preoral lobe feebly developed; oral sucker wide, 52±70 long and 65±95 wide, with massive, wide posterior appendage (solid prolongation) , not reaching to pharynx. Oral sucker armed with 55±61 circumoral spines arranged in two complete rows each of 27±31 spines. Spine patterns 271 28 (n 51); 281 28 (n 54); 291 29 (n 51); 311 30 (n 51). Anterior spines longer (12±15 long and 3 wide) than posterior ones (10±13 long and 2±3 wide). Prepharynx 62±110 long; pharynx oval, 32±45 long and 35±40 wide; oesophagus relatively long, almost as long as prepharynx. Intestinal caeca short and wide, terminating at distance anterior to ventral sucker. Ventral sucker spherical, well-developed, postequatorial, 50±60 in diameter. Sucker ratio 150.70±0.90. Testes symmetrical, near posterior extremity, 32±50 long and 30±40 wide. Ventrogenital sac feebly developed. Mouth of ventrogenital sac a slit-like opening, anterior to ventral sucker. Gonotyl present, without refractile bodies. Primordium of ovary postacetabular . Four pairs of ¯ame cells observed: ®rst pair anterior to pharynx, second between pharynx and intestinal caeca, third anterior to ventral sucker and fourth at level of excretory bladder. Excretory bladder X-shaped with short and wide arms. Second intermediate host. Garmanella pulchra (Cyprinodontidae). Site of infection. Mesenteries. Distribution. YucataÂn (Mitza near Progreso). References from Mexico. Present study. Specimens deposited. CHCM-353, CNHE 3935, IPCAS D-448, USNPC 90188. Comments. Metacercariae found in Garmanella pulchra resemble those of Ascocotyle (A.) sexidigita Martin and Steele, 1970, and A. (A.) gemina Font, Heard and Overstreet, 1984, two taxa supposed to be sibling species (Font et al., T. Scholz et al. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1736 Fig. 1. (A±D) Ascocotyle (Ascocotyle) gemina. Metacercariae from the mesentery of Garmanella pulchra, Mitza, YucataÂn. Spination patterns of circumoral spines 281 28 (A), 311 30 (B), and 291 29 (D). (E ) Ascocotyle (Phagicola) diminuta. Adult from the intestine of Ardea herodias, CelestuÂn, YucataÂn. Note 161 2 circumoral spines (additional spines on the dorsal side dotted). (F ) Ascocotyle (Leighia) chandleri. Metacercaria from the mesentery of Cyprinodon variegatus, Galveston Bay, Texas (paratype USNPC 54894) ; note 231 23 circumoral spines. (G) Ascocotyle (Phagicola) nana. Encysted metacercaria from the intestinal wall of Cichlasoma fenestratum, Catemaco Lake, Veracruz. (A) Excysted metacercaria, dorsal view; (B, E, F ) anterior end, dorsal view; (C, G) encysted metacercaria; (D) detail of circumoral spines. 1984a) . The species can be distinguished one from another by the number of refractile bodies within the gonotyl, the course of the uterus, average size of eggs, and infectivity of metacercariae of A. gemina for Cyprinodon variegatus LaceÂpeÁde but Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1737 not for Fundulus parvipinnis Girard, the type host of A. sexidigita, described from California (Martin and Steele, 1970; Font et al., 1984a). All but one of the diŒerential characters mentioned above are present only in adult worms and they cannot be applied to metacercariae that lack pockets within the gonotyl, their uterine loops are not completely formed and no eggs are present. The species of ®sh intermediate hosts of both trematode taxa (Cyprinodon variegatus or Fundulus parvipinnis, respectively) cannot be used for identi®cation either because none of these ®sh occur in the locality under consideration. Nevertheless, the absence of the metacercariae in two species of Fundulus (F. grandissimus Hubbs, F. persimilis Miller) from CheleÂm lagoon connected with Mitza swamp suggests that they belong to A. gemina rather than to A. sexidigita. In addition, Garmanella pulchra is closely related to Cyprinodon variegatus whereas it is distantly related to, and ecologically diŒerent from Fundulus parvipinnis, a speci®c intermediate host of A. (A.) sexidigita ( K. J. Lazara, personal communication) . Further, the metacercariae of A. (A.) gemina also encyst in the mesenteries ( Font et al., 1984a) , whereas those of A. (A.) sexidigita encyst within the wall of the intestine (Martin and Steele, 1970; Yoshino, 1972 ). For the reasons mentioned above, the metacercariae found in the mesentery of G. pulchra from Mexico are tentatively assigned to A. gemina until adult worms are available to con®rm speci®c identi®cation. Font et al. (1984a) elucidated the life cycle of this trematode, reporting the hydrobiid snail, Littoridinops monroensis ( Frauenfeld ), as the ®rst, the sheepshead minnow, Cyprinodon variegatus, as the second intermediate, and the clapper rail, Rallus longirostris Boddaert, as the de®nitive hosts of this parasite in Louisiana and Mississippi. Conti et al. (1986) and SepuÂlveda et al. (1999) found adults of A. gemina in reddish and great egrets (Egretta rufescens (Gmelin) and Casmerodius albus (Linnaeus), respectively) from Texas and Florida. Ascocotyle (Ascocotyle) leighi Burton, 1956 Metacercaria Morphology . Sogandares-Berna l and Lumsden (1964) did not describe metacercariae found in Mexico. Second intermediate hosts. Belonesox belizanus Kner, Poecilia sphenops Valenciennes in Cuvier and Valenciennes (Poeciliidae). Site of infection. Heart. Distribution. YucataÂn (Progreso). References from Mexico. Sogandares-Berna l and Lumsden (1964). Specimens deposited. None. Comments. Sogandares-Berna l and Lumsden (1964) found metacercariae of A. (A.) leighi in two poeciliid ®sh from Progreso, YucataÂn, most probably from CheleÂm lagoon. However, the authors did not provide any data on the morphology of metacercariae. Metacercariae of A. (A.) leighi are encysted exclusively in the heart and they have been found in poeciliid and cyprinodonti d ®sh in the USA and Mexico (Burton, 1956; Sogandares-Berna l and Bridgman, 1960; Sogandares-Berna l and Lumsden, 1964 ). They diŒer from those of A. (A.) tenuicollis encysted in the heart as well mainly in the number of circumoral spines (48±52 in total, i.e. 24±26 in each row, in the former taxon versus 32, i.e. 161 16 in A. (A.) tenuicollis) (Burton, 1956, 1958; Scholz et al., 1997a). Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1738 T. Scholz et al. Salgado-Maldonad o and Kennedy (1997 ), and Salgado-Maldonad o et al. ( 1997 ) reported metacercariae of A. (A.) leighi from the gills, mesenteries, heart and kidney of several species of cichlids from southeastern Mexico. Although few reference specimens were preserved and available to the present authors, it is possible to assume that most, if not all, metacercariae previously reported as A. leighi were misidenti®ed and belonged to other species of the Ascocotyle-complex. Metacercariae from internal organs of cichlid, characid and poeciliid ®sh were conspeci®c with A. (P ). nana and those encysted in the gills of cichlids with A. (A.) nunezae. Metacercariae encysted in the heart of ®sh of diŒerent families might belong to A. (A.) leighi but all voucher specimens examined were conspeci®c with A. (A.) tenuicollis. Adult trematodes of A. (A.) leighi are not known from Mexico because specimens found in the intestine of Casmerodius albus from PaÂtzcuaro Lake (MichoacaÂn), identi®ed by G. PeÂrez Ponce de LeoÂn as A. leighi (Lamothe-Argumedo et al., 1997; CNHE 1532), belonged in fact to A. (A.) tenuicollis (®gure 2). Ascocotyle (Ascocotyle) tenuicollis Price, 1935 (®gure 2) Metacercaria Morphology . Aguirre-Macedo and GarcõÂa-MaganÄa (1994: 17; ®gure 7a, b), Scholz et al. (1995: 179; ®gure 3A, C±E) and Scholz et al. (1997a: 163; ®gure 1E±G, Fig. 2. Ascocotyle (Ascocotyle) tenuicollis. Adults from the intestine of Casmerodius albus, PaÂtzcuaro Lake, MichoacaÂn, misidenti®ed as Ascocotyle leighi (CNHE 1532). (A) Total view, ventrally; (B) anterior end (spines of the posterior row on the dorsal side not ®gured); (C, D) detail of the terminal genitalia, ventral and lateral views, respectively. Abbreviations: ed, ejaculatory duct; eg, eggs; g, gonotyl; gp, genital pore; ic, intestinal caecum; mvs, mouth of ventrogenital sac; oe, oesophagus; ph, pharynx; sv, seminal vesicle; u, uterus; vf, vitelline follicles; vs, ventral sucker. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1739 I ) provided detailed descriptions of metacercariae that can easily be distinguished from those of other Ascocotyle species by combination of the following features: cyst spherical, thin-walled; body pyriform; preoral lobe prominent; posterior appendage long, curved to convoluted, reaching to pharynx or overlapping it; oral sucker with 32 circumoral spines forming two complete rows of 16 spines each; intestinal caeca short, very wide, sacciform, preacetabular, containing discoidal corpuscles; excretory bladder voluminous, ®lled with large lipoid droplets. Second intermediate hosts. Astyanax fasciatus (Cuvier), Bramocharax caballeroi Contreras-Balderas and Rivera-Teillery (Characidae) ; Poecilia catemaconis Miller, P. latipunctata Meek, P. mexicana Steindachner, P. petenensis (GuÈnther), P. velifera ( Regan), Poeciliopsis catemaco Miller ( Poeciliidae); Cichlasoma argentea Allgayer, C. aureum (GuÈnther), C. fenestratum (GuÈnther), C. friedrichstahl i (Heckel ), C. geddesi ( Regan), C. helleri (Steindachner), C. intermedium (GuÈnther), C. lentiginosum (Steindachner), C. managuense (GuÈnther), C. nourissati (Allgayer), C. octofasciatum (Regan), C. pearsei ( Hubbs), C. salvini (GuÈnther), C. synspilum Hubbs, C. urophthalmus (GuÈnther), Cichlasoma sp., Petenia splendida (GuÈnther) (Cichlidae); Ophisternon aenigmaticum Rosen and Greenwood (Synbranchidae) . Site of infection. Heart, exceptionally gill arches. Distribution. Campeche ( El Vapor, El Viento, La Pera, Palizada, Rancho II, Santa Gertrudis) ; Chiapas (Cedros, LacanjaÂ); Quintana Roo (Bacalar, Box Toro, CabanÄas, Cenote Azul, Escondido, FramboyaÂn, La UnioÂn, Laguna Paiyegua, Mahahual, Ramonal, Raudales, RõÂo Hondo); Tabasco (Camellones Chontales, El Espino, Puyacatengo, Santa Anita, Tucta, YumkaÂ); Veracruz (Catemaco, Los TuxtlasÐBalzapote, La Palma, Las MaÂquinas); YucataÂn (CelestuÂn, Chaamac, Chen-haÂ, DzibilchaltuÂn, Mitza, Noc-choncunchey, Sahkaba) . References from Mexico. Aguirre-Macedo and GarcõÂa-MaganÄa (1994); Scholz et al. (1995, 1997a) ; Salgado-Maldonad o et al. (1997); Scholz and Vargas-VaÂzquez (1998 ); Vidal-MartõÂnez et al. (2000); present study. Specimens deposited. CHCM-137, IPCAS D-345. Adult Morphology . Scholz et al. (1997a: 163 and 165; ®gure 1A±D, H ) described adults from naturally and experimentally infected de®nitive hosts. The adult of A. (A.) tenuicollis from the intestine of Casmerodius albus Linnaeus from PaÂtzcuaro Lake (MichoacaÂn), previously misidenti®ed as A. leighi (CNHE 1532Ðsee Comments), is illustrated in ®gure 2. DeWnitive hosts. Ardea herodias, Casmerodius albus, Buteogallus anthracinus (Deppe), Phalacrocorax olivaceus (Humboldt). Site of infection. Intestine. Distribution. Jalisco (Salinas de Careyes), MichoacaÂn (PaÂtzcuaro), YucataÂn (CelestuÂn). References from Mexico. Aguirre-Macedo and GarcõÂa-MaganÄa (1994); Scholz et al. (1997a) ; present study. Specimens deposited. CHCM-361, IPCAS D-344. Comments. Cichlids are the most suitable second intermediate hosts but ®sh of other families may also harbour metacercariae that are normally encysted within the bulbus of the heart (Scholz et al., 1997a) . Adults have been found in four species of ®sh-eating birds in Mexico, two of which (A. herodias and P. olivaceus) are new de®nitive hosts of this parasite. SepuÂlveda et al. (1999) found A. (A.) tenuicollis to Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1740 T. Scholz et al. belong to the most frequent (prevalence 54%) and numerous (mean intensity of infection 112 specimens; range 1±1260) helminth parasites of Casmerodius albus in Florida. Ascocotyle (Leighia) chandleri Lumsden, 1963 (®gure 1F ) Metacercaria Morphology . Metacercaria of this species found in Mexico was described by Scholz et al. (1997a: 166; ®gure 2F±H ). The authors identi®ed this metacercaria as A. (L .) chandleri on the basis of the presence of 281 29 circumoral spines, a large, branched excretory bladder, the morphology of the terminal genitalia with a large, pad-like gonotyl with several refractile bodies, the anterior position of the testes and the site of infection in the second intermediate host belonging to the same family as the type host, Cyprinodon variegatus. Second intermediate host. Fundulus persimilis (Cyprinodontidae). Site of infection. Intestinal wall. Distribution. YucataÂn (CheleÂm lagoon). References from Mexico. Scholz et al. (1997a). Specimens deposited. IPCAS D-352. Comments. Only one metacercaria was found during a study on the species of Ascocotyle parasitizing ®sh in southeastern Mexico (Scholz et al., 1997a) . Since it was partially damaged and studied within the cyst, new material is necessary to con®rm the occurrence of A. (L .) chandleri in Mexico. Ascocotyle (L .) chandleri was described from metacercariae encysted in the liver of Cyprinodon variegatus (Cyprinodontidae) and Mollienesia latipinna ( 5 Poecilia latipinna (Lesueur)) from Texas, USA (Lumsden, 1963). This author also found an immature worm, supposedly conspeci®c with A. (L .) chandleri, in the great egret (Casmerodius albus). Lumsden (1963) reported 54 circumoral spines in A. (L .) chandleri forming two circlets of 27 spines each but examination of a paratype from Cyprinodon variegatus ( USNPC 54894) revealed the presence of only 46 ( 231 23) spines (®gure 1F ), indicating variation in the number of spines in this species. Adults of this trematode were ®rst found in the roseate spoonbill (Ajaia ajaja ( 5 Platalea ajaja Linnaeus)) from Texas (Dronen, 1985). SepuÂlveda et al. (1996 ) reported A. (L .) chandleri from the little blue heron (Egretta caerulea (Linnaeus)) from Florida, with high values of prevalence (45%) and mean intensity of infection (385 specimens; range 1±3986). Although Yamaguti (1971) placed this species within the nominotypical subgenus Ascocotyle, its morphology (vitelline follicles between the ventral sucker and testes, the uterus reaching anteriorly to the pharynx, long intestinal caeca reaching to the testes) corresponds to the diagnosis of the subgenus Leighia as proposed by Sogandares-Berna l and Lumsden (1963). Therefore, this species is considered here to be a member of the subgenus Leighia. *Ascocotyle (Leighia) mcintoshi Price, 1936 (®gures 3, 4) Metacercaria Morphology. (Morphology based on ®ve ¯attened specimens from Xiphophorus sp.) Cyst large, oval to almost spherical, 420±432 in diameter, surrounded by thick 1741 Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae Fig. 3. Ascocotyle (Leighia) mcintoshi. (A, B, D±F ) Metacercariae from the mesenteries of Xiphophorus sp. (A, D) and Poecilia mexicana (B, E, F ), RõÂo Las MaÂquinas, Veracruz. (C, G) Adults from chick experimentally infected with the mesenteries of Xiphophorus sp., 2 days post infection. (A) Total view of excysted metacercaria, ventrally; (B) encysted metacercaria; (C ) total view of adult, ventrally; (D) terminal genitalia, ventrally (for abbreviations see ®gure 2); (E±G) circumoral spines (E, FÐ211 21 spines; in F only spines on the ventral side ®gured; GÐ201 20; dorsal view). In (A) and (B), cells with granular content ®gured only partly. layer of host tissue and thick (thickness 17±20), mechanically resistant, hyaline internal layer. Body of metacercaria pyriform, 1036 ±1560 long and 416±556 wide, covered with tegumental spines. Most part of body ®lled with numerous small, transversely oval brownish droplets ( lipoid?). Preoral lobe prominent; oral sucker subterminal, 35±70 long and 36±77 wide; posterior appendage conical, often curved or bent, not reaching to pharynx. Oral sucker surrounded with 38±42 circumoral spines forming two complete rows of 19±21 spines each; spination pattern 191 19 (n 51) and 211 21 (n 53). Anterior spines 12±18 long and 4±7 wide; posterior spines 9±12 long and 3±5 wide. Prepharynx 86±278 long; pharynx oval, 52±70 long and 45±80 wide; oesophagus slightly shorter than prepharynx. Caeca long and narrow, surrounding ventral sucker and reaching to ovary, slightly curved medially. Ventral sucker almost spherical, slightly postequatorial, 40±87 long and 55±80 wide. Sucker T. Scholz et al. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1742 Fig. 4. Ascocotyle (Leighia) mcintoshi. Metacercariae from the gills (?) of Xiphophorus sp., Laguna Azul, Los Tuxtlas, Veracruz (A, D) and the heart (?) of Poecilia mexicana, RõÂo La Palma, Veracruz (B, C, EÐcontracted specimen). (A, C ) Total view of excysted metacercaria, dorsally; (B, D) anterior end (spination pattern 201 20 in B; in D some spines lost); ( E) terminal genitalia, dorsally. In (C ), cells with granular content ®gured only on one side. ratio 150.95±1.62. Testes symmetrical, close to posterior extremity, 37±170 long and 92±232 wide. Genital sac well-developed, with numerous out-pocketings , anterosinistral to acetabulum, containing very large gonotyl with 8±11 prominent refractile bodies. Mouth of ventrogenital sac slit-like, transversely oval, anterolateral to ventral sucker. Primordium of ovary postacetabular , transversely oval, 50 long and 112 wide. Excretory bladder X-shaped, with short and wide arms, laterally branched in posterior part. Second intermediate hosts. Poecilia mexicana, Xiphophorus sp. (Poeciliidae). Site of infection. Mesenteries, occasionally heart (?) and gills (?). Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1743 Distribution. Veracruz (Los TuxtlasÐLa Palma, Laguna Azul, Las MaÂquinas). References from Mexico. Present study. Specimens deposited. CHCM-354, CNHE 3930, IPCAS D-399. Adult Morphology . (Morphology based on ®ve hot-formali n ®xed specimens from experimentally infected chick; 2 days post infection.) Body elongate, tapering towards anterior extremity, 820±980 long and 270±300 wide, entirely covered with scale-like tegumental spines. Preoral lobe prominent, conical, long; oral sucker subterminal, 50±55 long and 47±57 wide; posterior appendage long, often sinuous, not reaching to pharyngeal level. Sucker armed with 38±42 circumoral spines forming two complete rows of 191 19 (n 51); 201 20 (n 52); and 211 21 (n 52) spines each. Anterior spines 14±17 long and 4±6 wide; posterior spines 9±12 long and 3±4 wide. Prepharynx 40±125 long; pharynx muscular, oval to spherical, 55±72 long and 37±45 wide; oesophagus short. Intestinal caeca narrow, long, reaching posteriorly to excretory bladder, slightly curved medially at ovarian level. Ventral sucker spherical to transversely oval, slightly postequatorial, 55±67 long and 57±67 wide. Sucker ratio 151.09±1.35. Testes symmetrical, close to posterior extremity, 60±102 long and 80±125 wide. Seminal vesicle posterolateral to ventral sucker, C-shaped, 28 long and 36 wide. Ventrogenital sac formed, containing very large, pad-like gonotyl with 10±12 refractile bodies. Mouth of ventrogenital sac large, slit-like. Genital pore anterosinistral to ventral sucker. Ovary dextral, nearly spherical, posterolateral to seminal vesicle, 60±70 long and 70±92 wide. Seminal receptacle voluminous, mediolateral to ovary, 62±87 long and 73±87 wide. Uterus sinuous; uterine loops anteriorly reaching to pharyngeal level, posteriorly crossing testes and reaching to posterior margin of ovary. Vitellarium forming two long lateral bands of vitelline follicles starting at acetabular level anteriorly and passing testes posteriorly. Eggs (n 530) operculate, 21 (19±22) long and 11 (9±13) wide. Excretory bladder voluminous, laterally branched; excretory pore terminal. DeWnitive host. Chick (experimental ). Site of infection. Intestine. Distribution. Not known. References from Mexico. Present study. Specimens deposited. CHCM-354, CNHE 3929, IPCAS D-447, USNPC 90190. Comments. Metacercariae found in this study did not diŒer from those of A. (L .) mcintoshi as described by Leigh ( 1974) from Gambusia anis Baird and Girard and Poecilia latipinna. Both ®sh species from Mexico represent new second intermediate hosts. Dominant site of infection of metacercariae found in this study were the mesenteries but one specimen (®gure 4A, D) was reported to occur in the gills (? musculature of gill arches) and another one (®gure 4B, C ) in the heart (?). Stein (1968) reported metacercariae of this trematode from the liver of G. anis in Florida but Leigh (1974 ) found them in various organs such as mesenteries adjacent to the small intestine, attached to the visceral peritoneum, and in the liver, gall bladder and fat bodies. Experimentally recovered adult trematodes were almost identical with those of A. (L .) mcintoshi as described by Price (1936 ), Yamaguti ( 1971) and Leigh ( 1974). SepuÂlveda et al. (1996, 1999) found this trematode to be a relatively common parasite of the little blue heron (Egretta caeruleaÐprevalence 29%; mean intensity Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1744 T. Scholz et al. 84; range 1±963 specimens) but quite rare (prevalence 6%, mean intensity seven specimens) parasite of the great egret (Casmerodius albus) in Florida. Ostrowski de NuÂnÄez (1992) described Ascocotyle (Leighia) hadra, a sibling species of A. (L .) mcintoshi, from Argentina. Both taxa diŒer one from another in only a few biological and morphological characteristics, most of them being related to cercariae (see Ostrowski de NuÂnÄez, 1992). Metacercariae can be distinguished by the absence of pigmentation in the former species (versus brownish colour of metacercariae of A. (L .) mcintoshi ) and diŒerent spectrum of second intermediate hosts: A. (L .) mcintoshi infects Gambusia anis whereas A. (L .) hadra only poeciliid ®shes native to Argentina, Cnesterodon decemmaculatus (Jenyns) and Jenynsia lineata (Jenyns). Adults diŒer in body size (496±798 in A. (L .) hadra versus 680±1200 in A. (L .) mcintoshi and in the number of projections of the gonotyl (10±11 versus 13). The specimens found in Mexico correspond to A. (L .) mcintoshi in brownish pigmentation of metacercariae, the larger size of adults and the spectrum of ®sh intermediate hosts. Geographical distribution also supports conspeci®city of material from YucataÂn with A. (L .) mcintoshi. The number of digital projections (pockets) of the gonotyl in the present material (8±11 in metacercariae and 10±12 in adults) was more similar to that reported for A. (L .) hadra. However, variability of this character and diculties in counting precise number of projections cast doubts upon reliability of this feature to distinguish taxa that possess numbers of pockets that are not markedly diŒerent. Consequently, the specimens studied by the present authors are identi®ed as A. (L .) mcintoshi. Ascocotyle (L .) mcintoshi was described from white ibis, Guara alba ( 5 Eudocimus albus (Linnaeus)), from Florida by Price (1936) and then reported by Stein (1968), Leigh (1974) and SepuÂlveda et al. (1996, 1999) from the USA. The life cycle of this trematode was elucidated by Leigh ( 1974) who found the prosobranch snail Littoridinops monroensis to serve as the ®rst intermediate host, in which ophthalmogymnocephalou s cercariae developed. The present ®nding is the ®rst record of A. (L .) mcintoshi from Mexico. Ascocotyle (Leighia) megalocephala Price, 1932 (®gure 5A±D) Metacercaria Morphology . Scholz et al. (1995: 179±180; ®gure 4) had described a metacercaria designated as Ascocotyle (Ascocotyle) sp. 1 that was later identi®ed as A. (L .) megalocephala by Scholz et al. (1997a) . A description of six metacercariae from Poecilia mexicana is provided: cyst widely oval to almost spherical, 432±472 long and 288±368 wide, with thick outer wall, often brownish, and thinner internal wall. Metacercarial body ¯ask-shaped, slightly tapering towards anterior end, 376±700 long and 220±330 wide, densely covered with simple tegumental spines. Spines almost completely covering ventral side of body except for small area around subterminal excretory pore; dorsally, spines reaching only to level of excretory bladder. Remnants of eye-spot granules scattered at pharyngeal level. Preoral lobe feebly developed (®gure 5A) but in some living specimens may be protruded (®gure 5C, D). Oral sucker spherical, 67±97 long and 80±140 wide, with conical posterior appendage, usually not reaching to pharynx, sometimes curved. Oral sucker armed with 74±80 ®ne but well-visible circumoral spines arranged in two complete rows of 36±40 spines each; anterior spines 12±17 long and 3±4 wide; posterior spines 1745 Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae Fig. 5. (A±D) Ascocotyle (Leighia) megalocephala. Metacercariae from the external surface of the intestine of Poecilia velifera, Chen-ha cenote, YucataÂn (A) and P. mexicana, Balzapote, Veracruz (B±D). (E, F ) Galactosomum puni. Adult from the intestine of Larus occidentalis, Isla Rasa, Baja California (CNHE 804). (A) Total view, ventrally; (B) encysted metacercaria; (C ) circumoral spines (391 39); (D) anterior end (only spines on the ventral side ®gured); (E, F ) terminal genitalia, more internal (E ) and external (F ) views, ventrally. Note presence of hermaphroditic duct (hd) in (E ) and a slit-like opening (mouth) of the ventrogenital sac (mvs; for other abbreviations see ®gure 2) in (F ). 10±16 long and 3±4 wide. Spination pattern 361 38 (n 51); 371 38 (n 51); 381 39 (n 51); 391 39 (n 52); 401 40 (n 51). Prepharynx 80±102 long; pharynx oval to almost pyriform, 40±72 long and 30±52 wide; oesophagus very short or indistinct. Intestinal caeca short and wide, often forming a sac, reaching only to anterior margin of ventral sucker. Ventral sucker spherical, postequatorial, 68±90 long and 62±80 wide. Sucker ratio 150.55±0.80. Testes symmetrical, at distance from posterior Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1746 T. Scholz et al. extremity, 37±80 long and 30±55 wide. Ventrogenital sac feebly developed, with simple, pad-like, transversely oval gonotyl. Primordium of ovary anteromedial to testes. Excretory bladder voluminous, X-shaped to sac-like, in encysted metacercariae occupying more than half of metacercarial body, ®lled with large droplets. Excretory pore subterminal, ventral. Second intermediate hosts. Poecilia mexicana, P. velifera (Poeciliidae). Site of infection. Wall of stomach and intestine, mesenteries. Distribution. Veracruz ( Los TuxtlasÐarroyo Balzapote); YucataÂn (Mitza, Sahkaba). References from Mexico. Scholz et al. (1995 Ðas Ascocotyle (A.) sp. 1); Scholz et al. (1997a) ; present study. Specimens deposited. CHCM-356a, CNHE 3925, IPCAS D-351, USNPC 90189. Adult Morphology . No substantial diŒerences were observed between the specimen found in Ardea herodias from CelestuÂn and that described by Scholz et al. (1997a: 176, 178; ®gure 7A, B, D) from the intestine of Casmerodius albus from the same locality. Therefore, only a brief description of newly collected specimen is provided here: body 800 long and 360 wide. Oral sucker 125 long and 197 wide. Sucker armed with simple spines forming two rows, with 38 spines in anterior complete row; posterior row with several spines apparently missing, most probably containing 38 spines as well. Anterior spines 25 long and 6 wide; posterior spines 21±22 long and 5±6 wide. Ventral sucker 56 long and 55 wide. Sucker ratio 150.34. Testes 107±115 long and 137±160 wide. Ovary 100 long and 140 wide. Seminal receptacle 87 long and 97 wide. Eggs 19±21 long and 9±11 wide. DeWnitive host. Ardea herodias, Casmerodius albus. Site of infection. Intestine. Distribution. YucataÂn (CelestuÂn). References from Mexico. Scholz et al. (1997a) ; present study. Specimens deposited. CHCM-356, CNHE 3925, IPCAS D-446. Comments. Two species of Poecilia from Mexico represent new ®sh hosts of A. (L .) megalocephala. Stein (1968 ) reported the poeciliid Mollienisia latipinna ( 5 Poecilia latipinna) as its natural intermediate host in Florida but he did not provide descriptions or ®gures of the metacercariae. Ascocotyle (L .) megalocephala was described by Price (1932 ) from Butorides sp. from Puerto Rico. Up to date, adults have been found only in Puerto Rico (type locality) and Mexico (Price, 1932; Scholz et al., 1997a) . The heron Ardea herodias is a new de®nitive host of this trematode that seems to be a rare parasite of herons. Ascocotyle (Leighia) nunezae Scholz, Vargas-VaÂzquez, Vidal-MartõÂnez and Aguirre-Macedo, 1997 Metacercaria Morphology . Scholz et al. (1995: 184; ®gure 8A±GÐas Ascocotyle (Phagicola) sp. 3) and Scholz et al. (1997b: 143; ®gures 9±15) provided detailed descriptions of metacercariae. The most typical characters enabling diŒerentiation of A. (L .) nunezae from congeners are as follows: body elongate to conical, tapering anteriorly, entirely spined; preoral lobe feebly developed; posterior appendage conical, not reaching to pharynx; circumoral spines forming one complete row of 25±26 and seven to nine Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1747 accessory spines on dorsal side; intestinal caeca long, reaching to ovarian primordium, slightly curved medially around ventral sucker. Second intermediate hosts. Cichlasoma aureum, C. helleri, C. meeki (Brind ), C. octofasciatum, C. pasionis Rivas, C. pearsei, C. robertsoni Regan, C. salvini, C. synspilum, C. urophthalmus, Petenia splendida (Cichlidae). Site of infection. Gills. Distribution. Campeche ( El Viento, La Pera, Palizada, Rancho II, Santa Gertrudis, Zoh Laguna); Chiapas (LacanjaÂ); Quintana Roo (Box Toro, CabanÄas, La UnioÂn, Laguna Paiyegua, Los Cuates, Ramonal, Raudales, RõÂo Hondo); Tabasco (Las Ilusiones, Puyacatengo, Yucateco, YumkaÂ); YucataÂn (Chaamac, Chek-haÂ, Dzonot Cervera, Noc-choncunchey, Petentuche) . References from Mexico. Scholz et al. (1995 Ðas Ascocotyle (Phagicola) sp. 3); Scholz et al. (1997a, 1997b ); Scholz and Vargas-VaÂzquez (1998); Vidal-MartõÂnez et al. (2000 ); present study. Specimens deposited. CNHE 3729, 3731, IPCAS D-349. Adult Morphology . Adults from naturally and experimentally infected de®nitive hosts from Mexico were described and illustrated by Scholz et al. (1997b: 141, 143; ®gures 1±8). DeWnitive hosts. Casmerodius albus (natural ); chicks (experimental ). Site of infection. Intestine. Distribution. YucataÂn (CelestuÂn). References from Mexico. Scholz et al. (1997b ). Specimens deposited. CNHE 2849 (holotype); BMNH 1996.10.7.5; CHCM 185; IPCAS D-348; USNPC 86819 ( paratypes) . Comments. Numerous recent ®ndings of metacercariae from cichlid ®sh do not correspond with the fact that adults have been found only once in naturally infected hosts. In Ardea herodias from the type locality examined by the present authors, A. (L .) nunezae was not found, similarly during a large-scale survey of the parasites of the little blue heron (Egretta caerulea) and great egret (Casmerodius albus) carried out in Florida by SepuÂlveda et al. (1996, 1999). As pointed out by Scholz et al. (1997b ), A. (L .) nunezae possesses features that place it in the intermediate position among Ascocotyle subgenera. Scholz et al. (1997b ) placed this species to the nominotypical subgenus Ascocotyle following Yamaguti’s (1971 ) concept of the subgenera of Ascocotyle. However, the authors overlooked that members of the subgenus Ascocotyle have the uterus con®ned mainly to the postacetabula r area whereas those of Leighia in its original concept by Sogandares-Berna l and Lumsden (1963) possess uterine loops reaching anteriorly to the pharyngeal level. Therefore, A. nunezae is transferred to the subgenus Leighia. *Ascocotyle (Phagicola) ampullacea Miller and Harkema, 1962 (®gure 6) Metacercaria Morphology. (Morphology based on one specimen from Gambusia yucatana Regan, two from Poecilia sphenops, one from Poecilia sp. and two from Belonesox belizanus.) Cyst large, almost spherical, 342±365 long and 335±365 wide, with thick (13±20), mechanically resistant and elastic outer wall, and thin, transparent internal T. Scholz et al. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1748 Fig. 6. Ascocotyle (Phagicola) ampullacea. Metacercariae from the muscles of Gambusia yucatana, El Yucateco, Tabasco (A), gonads of Belonex belizanus, Chaamac cenote, YucataÂn (B, D, F ), mesentery of Poecilia sp., El Yucateco, Tabasco (C ), and intestinal wall of Poecilia sphenops, Mitza, YucataÂn (E, G). (A, B) Total view of excysted metacercaria, dorsally; (C ) encysted metacercaria; (D) anterior end, dorsal view; (E, F ) terminal genitalia, dorsal view; (G) circumoral spines; small tegumental, scale-like spines ®gured only on one side. wall. Body ¯ask-shaped, tapering anteriorly, 490±670 long and 230±279 wide, covered with small tegumental spines becoming smaller posteriorly. Preoral lobe indistinct; oral sucker spherical, subterminal, 45±47 long and 42±51 wide, with short, conical posterior appendage, not reaching to pharynx. Oral sucker armed with 44±54 circumoral spines forming two complete rows each of 22±27 spines each. Spination patterns 221 22 (n 52); 251 23 (n 51); 251 25 (n 52); 271 27 (n 51). Anterior spines 10±12 long and 2 wide; posterior spines 9±11 long and 2 wide. Prepharynx 35±120 long; pharynx oval, 42±47 long and 32±42 wide; oesophagus relatively short. Intestinal caeca long and narrow, surrounding ventral sucker, terminating anterior to excretory bladder, containing numerous spherical bodies. Ventral sucker spherical, slightly postequatorial, 58±62 long and 62±77 wide. Sucker ratio 15 1.48±1.83. Testes symmetrical, near posterior extremity, 35±50 long and 47±60 wide. Ventrogenital sac anterosinistral to ventral sucker, containing gonotyl with 12±14 refractile bodies. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1749 Primordium of ovary postacetabular . Flame cell pattern not determined but probably 16 ¯ame cells present, arranged in four pairs. First pair situated between mouth and pharynx, second pair at acetabular level, third between acetabulum and excretory bladder and fourth pair at level of excretory bladder. Excretory bladder X-shaped, with prominent anterior arms and reduced posterior ones, ®lled with spherical droplets. Second intermediate hosts. Belonesox belizanus, Gambusia yucatana, Poecilia sphenops, Poecilia sp. ( Poeciliidae). Site of infection. Muscles (G. yucatana), intestinal wall (P. sphenops), mesenteries (Poecilia sp.), gonads (B. belizanus). Distribution. Tabasco ( El Yucateco); YucataÂn (Chaamac, Mitza). References from Mexico. Present study. Specimens deposited. CNHE 3923, IPCAS D-400. Comments. Despite slight diŒerences in the size of the prepharynx and oesophagus, and the site of infection, all metacercariae found in poeciliids from Tabasco and YucataÂn are considered to be conspeci®c because of similar size and shape of cysts and their walls, a ¯ask-shaped body, an indistinct preoral lobe, a conical posterior appendage not reaching to the pharynx, armament of the oral sucker, long and narrow intestinal caeca, and the presence of more than 10 refractile bodies within the gonotyl. In all these features, the metacercariae ®t best into the diagnosis of the species A. (P.) ampullacea as described by Miller and Harkema ( 1962) from Procyon lotor (Linnaeus) from North Carolina and as observed in its paratypes ( USNPC 59584). It should be mentioned that refractile bodies within the gonotyl of adults of A. (P.) ampullacea were incorrectly described as spines by Miller and Harkema (1962). The only diŒerence was in slightly higher number of circumoral spines in some metacercariae (22±27 spines but mostly 22±25 spines) than in adults (20±24). However, this may be due to intraspeci®c variation in the number of spines. Stein ( 1968) ®rst reported metacercariae of this trematode from the the intestinal mesenteries and body musculature of the poeciliid ®sh Gambusia anis from Florida but the author did not provide any description or illustrations. Adults obtained from chicks fed with infected organs possessed 22 1 22 circumoral spines (Stein, 1968 ). The present ®ndings represent a new geographical record of this fairly rare trematode known only from the USA and Mexico. Ascocotyle (Phagicola) diminuta Stunkard and Haviland, 1924 (®gure 1E ) Metacercaria Morphology . Descriptions were provided by Scholz et al. ( 1995: 180±181; ®gures 5, 7B) and Scholz et al. (1997a: 172±173; ®gures 2A±E, 5A±D, F, 7E ). Metacercariae can be distinguished from those of congeneric species by the elongate shape of cyst, the presence of 18 massive circumoral spines arranged in one complete row of 16 spines and two smaller additional spines on the dorsal side, narrow and long intestinal caeca reaching posterior to the ventral sucker, and a simple gonotyl lacking refractile bodies. Second intermediate hosts. Belonesox belizanus, Poecilia latipunctata, P. mexicana, P. petenensis, P. sphenops, P. velifera (Poeciliidae); Cyprinodon artifrons Hubbs (reported as C. variegatus by Sogandares-Berna l and Lumsden, 1963), Fundulus Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1750 T. Scholz et al. grandissimus, F. persimilis, Floridichthys polyommus Hubbs (reported as F. carpio Hubbs by Scholz et al., 1997a) (Cyprinodontidae) . Site of infection. Gills. Distribution. Quintana Roo (Box Toro, Cenote Azul, Ramonal ); Veracruz (Los TuxtlasÐBalzapote); YucataÂn (Chaamac, Chek-haÂ, CheleÂm, Chen-haÂ, DzibilchaltuÂn, Noc-choncunchey, Progreso, Sahkaba) . References from Mexico. Sogandares-Berna l and Lumsden ( 1963Ðas Ascocotyle angrense); Scholz et al. (1995, 1997a) ; Scholz and Vargas-VaÂzquez (1998); present study. Specimens deposited. CHCM-358, IPCAS D-343. Adult Morphology . Scholz et al. (1997a: 173; ®gures 5E, G±I, 7F, G ) described adults from naturally and experimentally infected hosts. DeWnitive hosts. Ardea herodias, Casmerodius albus (natural ), chicks (experimental ). Site of infection. Intestine. Distribution. YucataÂn (CelestuÂn). References from Mexico. Scholz et al. (1997a) ; present study. Specimens deposited. CNHE 3924, IPCAS D-342, USNPC 88538, 90191. Comments. Metacercariae from the gill ®laments of poeciliid ®shes (Belonesox belizanus, Cyprinodon variegatus ( 5 C. artifrons) and Mollienisia sphenops ( 5 Poecilia sphenops)) from Progreso, YucataÂn, identi®ed by Sogandares-Berna l and Lumsden (1963) as Ascocotyle angrense, were undoubtedl y conspeci®c with A. (P.) diminuta because they possessed 161 2 circumoral spines (instead of 181 2 in A. (P.) angrense Ðsee Ostrowski de NuÂnÄez, 1993 and Scholz et al., 1997a). In Mexico and the USA, only poeciliid and cyprinodonti d ®sh serve as second intermediate hosts of A. (P.) diminuta (see Stunkard and Uzmann, 1955; SogandaresBernal and Bridgman, 1960; Stein, 1968; Scholz et al., 1997a) . In Argentina, Ostrowski de NuÂnÄez (1993 ) found ®sh of the families Cichlidae and Jenynsidae to be suitable second intermediate hosts. SepuÂlveda et al. (1999) found A. (P.) diminuta to be one of the most frequent parasites of the great egret (Casmerodius albus) from Florida, with prevalence of infection being 33% (n 570) and mean intensity 64 specimens (range 1±3580). Besides ®sh-eating birds, mammals such as raccoon, rats, mice and hamsters have been reported as de®nitive hosts of this trematode reported from a large area between northeastern USA (Connecticut, MD) and Argentina (Stunkard and Haviland, 1924; Stunkard and Uzmann, 1955; Ostrowski de NuÂnÄez, 1993). The life cycle of this trematode was ®rst elucidated by Ostrowski de NuÂnÄez (1993 ) who found the hydrobiid snails Littoridina castellanosae Gaillard and L . parchappi d’Orbigny to serve as the ®rst and cyprinodonti d ®sh as the second intermediate hosts in Argentina. Scholz et al. (1997a) successfully infected ®sh with cercariae of A. (P.) diminuta released from the hydrobiid snail Pyrgophorus coronatus (PfeiŒer) in YucataÂn. Ascocotyle (Phagicola) longa Ransom, 1920 (®gure 7) Metacercaria Morphology. (Morphology based on 26 specimens from Mugil cephalus Linnaeus and M. curema Valenciennes in Cuvier and Valenciennes.) Cyst widely oval, 1751 Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae Fig. 7. Ascocotyle (Phagicola) longa. Metacercariae from the heart of Mugil cephalus, RõÂo Cuitzmala, Jalisco (A±C ) and the musculature of gill arches of Dormitator latifrons, Marismas de Chalacatepec, Jalisco (F ), and adult from the intestine of Ardea herodias, CelestuÂn lagoon, YucataÂn ( E). (A) Total view of excysted metacercaria, dorsally; (B) encysted metacercaria; (C ) terminal genitalia, note bipartite gonotyl (g); (D±F ) circumoral spines (n516 ). (A, C ) Free-hand schematic drawing; not in scale. thin-walled, 154±286 long and 131±207 wide. Body pyriform, 323±554 long and 115±202 wide, covered with scale-like tegumental spines. Remnants of eye-spots posterior to pharynx. Region between pharynx and ventral sucker containing oval cells with granular contents (? gland cells). Preoral lobe moderately developed; oral sucker 36±54 long and 36±54 wide, with well-developed posterior appendage, often sinuous, only rarely reaching to pharynx. Oral sucker surrounded by one row of 16 massive circumoral spines (n 519), 9±15 long and 3±4 wide. Prepharynx 40±102 long; pharynx strongly muscular, 30±45 long and 23±34 wide; oesophagus relatively short. Intestinal caeca narrow and long, surrounding ventral sucker and primordium of ovary, curved medially at level of anterior branch of excretory bladder, ®lled with spherical corpuscles. Ventral sucker spherical, well-developed, postequatorial, 23±40 long and 23±37 wide. Sucker width ratio 150.71±0.90. Testes symmetrical, near Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1752 T. Scholz et al. posterior extremity, 27±50 long and 27±55 wide. Seminal vesicle two-chambered, postacetabular . Genital sac anterosinistral to acetabulum, containing bipartite gonotyl composed of two pad-like lobes (®gure 7C ). Primordium of ovary postacetabular , 18 long and 40 wide. Excretory bladder X-shaped, with short and wide arms, ®lled with numerous, dark granules. Flame cell formula most probably (posterior ducts not observed completely) 2 [(21 2 )1 (21 2)] 516. First ¯ame cells posterolateral to oral sucker; second at pharyngeal level; third at level of caecal bifurcation; fourth anterolateral to acetabulum; ®fth and sixth posterolateral to ventral sucker; seventh lateral to anterolateral to testes and eighth posteromedial to testes. Second intermediate hosts. Gobiesox Xuviatilis Briggs and Miller (Cyprinodontidae); Dormitator latifrons (Richardson) ( Eleotridae); Mugil cephalus, M. curema (Mugilidae) . Site of infection. Heart, musculature of gill branches, body musculature, rarely intestinal wall, liver, gonads, mesenteries. Distribution. Jalisco ( El JabalõÂ, Marismas de Chalacatepec, RõÂo Cuitzmala, Salinas de Careyes, San NicolaÂs). References from Mexico. Scholz (1999); present study. Specimens deposited. BMNH 2000.6.1.9, CHCM-352, CNHE 3928, IPCAS D-445, USNPC 88537, 90192, 90193. Adult Morphology . Scholz (1999) redescribed the species on the basis of examination of the type specimens and reference material from diŒerent hosts and geographical regions. DeWnitive host. Ardea herodias. Site of infection. Intestine. Distribution. YucataÂn (CelestuÂn). References from Mexico. Present study. Specimens deposited. CNHE 3926, IPCAS D-295. Comments. Metacercariae are frequent parasites of brackish-water ®sh, above all grey mullets (Hutton and Sogandares-Bernal , 1959, 1960; Manfredi and Oneto, 1997 ). In Mexico, they have been found only in ®sh from its western (Paci®c) coast (Scholz, 1999; present study) . Adults of A. (P.) longa found in a number of birds, mainly herons, and mammals (see Scholz, 1999 for review) are reported from Mexico for the ®rst time. Scholz (1999 ) synonymized A. (P.) arnaldoi Travassos, 1929, A. (P.) byrdi ( Robinson, 1956) and A. (P.) longicollis ( Kuntz and Chandler, 1956 ) with A. (P.) longa that is the most widely distributed species of Ascocotyle reported from North and South America, Europe, North Africa and Asia (Middle East) (see Scholz, 1999 for references). Chie et al. (1992) reported human infections caused by a species of Phagicola ( 5 Ascocotyle (Phagicola)), supposed to be A. (P.) longa by Manfredi and Oneto (1997 ). The latter authors discussed the capacity of this trematode to infect humans because of heavy infections of mullets with its metacercariae encysted in the muscles. Ascocotyle (Phagicola) macrostoma ( Robinson, 1956) Metacercaria Morphology . To date, no data on metacercarial morphology exist. Second intermediate host. Poecilia velifera (Poeciliidae). Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1753 Site of infection. ? Gill arches (see Comments). Distribution. YucataÂn (Chaamac). References from Mexico. Scholz et al. (1997a). Adult Morphology . Scholz et al. (1997a: 175±176; ®gure 6A±F ) redescribed this species on the basis of experimentally recovered adults. It is characterized mainly by the following features: a spindle-shaped body; a feebly developed anterior lobe; long, conical posterior appendage overlapping the pharynx; 18 massive, large ( length 24±33) circumoral spines arranged in one complete row; the intestinal caeca reaching to the ovarian level. DeWnitive host. Chick (experimental ). Site of infection. Intestine. Distribution. Not known (? YucataÂn). References from Mexico. Scholz et al. (1997a). Specimens deposited. IPCAS D-350. Comments. Stein (1968) fed chicks upon viscera ( liver and spleen) of the poeciliid Mollienisia latipinna ( 5 Poecilia latipinna) from Florida and found adults of A. (P.) macrostoma. However, no description or illustrations were provided and the morphology of metacercariae is still unknown. Observations of Stein (1968) cast doubts upon the site of infection of metacercariae A. (P.) macrostoma from YucataÂn, supposed to be encysted in the gills (Scholz et al., 1997a) . It seems that they may have been encysted in the internal organs rather than directly in the gill ®laments. Dronen (1985) reported adults of A. (P.) macrostoma from the intestine of the roseate spoonbill (Platalea ajaja) from Texas that may be the principal de®nitive host. Trematodes found in the same host from Florida and identi®ed by SepuÂlveda et al. (1994 ) as Phagicola longa ( USNPC 83030) may also be conspeci®c with A. (P.) macrostoma (unpublished data) but they lack circumoral spines to con®rm species identi®cation. Published data on the occurrence of A. (P.) macrostoma suggest its distribution being limited to southeastern USA and Mexico ( Robinson, 1956; Stein, 1968; Dronen, 1985; Scholz et al., 1997a). Ascocotyle (Phagicola) nana Ransom, 1920 (®gure 1G) Metacercaria Morphology . Metacercariae were described by Salgado-Maldonad o and AguirreMacedo (1991: 396±398, 400; ®gure 2), Aguirre-Macedo and GarcõÂa-MaganÄa (1994: 19±20; ®gure 8a, b; all as Phagicola angrense), Scholz et al. (1995 Ðas Ascocotyle (Phagicola) sp. 2: 181±182; ®gure 6, 7A) and Scholz et al. (1997a: 168; ®gure 3D±J ). The most typical characters are pyriform shape of body; indistinct preoral lobe; very short posterior appendage; ®ne circumoral spines forming one complete row of 16 (exceptionally 15 or 17) spines and four (rarely three to six) additional spines; long intestinal caeca curved medially around ventral sucker and reaching to excretory bladder; and well-developed gonotyl with numerous (about 15) refractile bodies (Scholz et al., 1997a). Second intermediate hosts. Astyanax fasciatus (Characidae); Cichlasoma argentea, C. aureum, C. belone ( Allgayer) ( 5 C. coeruleus (Stawikowski and Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1754 T. Scholz et al. Werner)), C. fenestratum, C. friedrichstahl i, C. geddesi, C. helleri, C. intermedium, C. managuense, C. meeki, C. nourissati, C. octofasciatum, C. pasionis, C. pearsei, C. salvini, C. synspilum, C. urophthalmus, Petenia splendida (Cichlidae); Gambusia yucatana, Poecilia petenensis, P. velifera, Xiphophorus sp. (Poeciliidae). Site of infection. Intestinal wall, gonads, liver, kidney, spleen, mesenteries, muscles, swimbladder, rarely gills, heart and brain. Distribution. Campeche (ChampotoÂn, El Vapor, El Viento, Estero Pargo, La Pera, Palizada, Santa Gertrudis); Chiapas (Cedros); Quintana Roo (Box Toro, CabanÄas, Cenote Azul, Escondido, Gran Cenote, La UnioÂn, Laguna Guerrero, Laguna OcoÂn, Los Cuates, Mahahual, Noh-Bek, Ramonal, Raudales, RõÂo Hondo, Valle Hermoso); Tabasco (BalancaÂn, Camellones Chontales, El Espino, El Guanal, El Yucateco, Jonuta, Las Ilusiones, Puyacatengo, Teapa, Tenosique, YumkaÂ); Veracruz (Catemaco) ; YucataÂn (CelestuÂn, Chaamac, Chek-haÂ, Chen-haÂ, DzibilchaltuÂn, Dzonot Cervera, FramboyaÂn, Hodz-ob, Mitza, Noc-choncunchey, Petentuche, Progreso, RõÂo Lagartos). References from Mexico. Salgado-Maldonad o and Aguirre-Macedo ( 1991); JimeneÂz-GarcõÂa (1993); Aguirre-Macedo and GarcõÂa-MaganÄa (1994Ðall authors as Phagicola angrense); Scholz et al. (1995 Ðas Ascocotyle (Phagicola) sp. 2); SalgadoMaldonado et al. (1997); Scholz et al. (1997a) ; Scholz and Vargas-VaÂzquez (1998); Vidal-MartõÂnez et al. (1998, 2000); present study. Specimens deposited. CHCM-123, CNHE 3728, IPCAS D-341, USNPC 90194. Adult Morphology . Adult worms from Mexico were described and illustrated by Salgado-Maldonad o and Aguirre-Macedo (1991 ), Aguirre-Macedo and GarcõÂaMaganÄa (1994: 20; ®gure 8c), and Scholz et al. (1997a: 168±170; ®gure 4). Scholz et al. (1997a) counted 161 4 circumoral spines in most ( 70%) of specimens studied; only a few trematodes possessed diŒerent spination patterns (141 4; 151 4; 161 5; 161 6; 171 4; 171 5). DeWnitive hosts. Ardea herodias, Buteogallus anthracinus, Casmerodius albus (natural ), chicks, laboratory mouse (experimental ). Site of infection. Intestine. Distribution. YucataÂn (CelestuÂn). References from Mexico. Salgado-Maldonad o and Aguirre-Macedo ( 1991); Aguirre-Macedo and GarcõÂa-MaganÄa (1994)Ðall as Phagicola angrense; Scholz et al. (1997a) ; present study. Specimens deposited. CHCM-359, IPCAS D-340, USNPC 86809, 90195. Comments. Cichlids, in particular Cichlasoma urophthalmus, are the most suitable hosts of this trematode that belongs to the most widely distributed species of ®sh parasites in southeastern Mexico. Its metacercariae are also common in perciform ®sh in the northern part of the Gulf of Mexico ( Mississippi, Florida) ( Font et al., 1984b ). Comments. The type host of A. (P.) nana is the arctic fox, Alopex lagopus (Linnaeus), and several mammals such as opossum, raccoon, Syrian hamster or mouse have been reported as experimental hosts (Ransom, 1920; Font et al., 1984b ). However, most adults obtained from natural de®nitive hosts were found in ®sheating birds such as Ardea herodias, Buteogallus anthracinus, Casmerodius albus, Ixobrychus exilis (Gmelin) and Sula bassana (Linnaeus) ( Font et al., 1984b; SalgadoMaldonado and Aguirre-Macedo, 1991; Scholz et al., 1997a; SepuÂlveda et al., 1999 ). Trematodes of the family Heterophyidae 1755 Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Cercariae of A. (P.) nana were found in the snail Pyrgophorus coronatus from YucataÂn (Ditrich et al., 1997 ). Ascocotyle (Phagicola) sp. (®gure 8) Metacercaria Morphology. (Morphology based on one specimen from Cichlasoma urophthalmus.) Body pyriform, markedly tapering anteriorly, 1240 long and 544 wide. Small unicellular glands situated laterally at acetabular level. Preoral lobe welldeveloped. Oral sucker subterminal, 78 long and 102 wide, armed with single row of 20 spines. Posterior appendage long, narrow and curved. Prepharynx 171 long. Pharynx strongly muscular, large, 71 long and 76 wide. Oesophagus very short. Intestinal caeca long, narrow, reaching to testes. Ventral sucker slightly postequatorial, 84 long and 92 wide. Sucker ratio 150.98. Testes large, symmetrical, near posterior extremity, 146±172 long and 182±198 wide. Ventrogenital sac Fig. 8. Ascocotyle (Phagicola) sp. Excysted metacercaria from ®ns of Cichlasoma urophthalmus, El Vapor, Campeche. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1756 T. Scholz et al. well-developed, containing large gonotyl 81 long and 154 wide, with 10 large, ®ngerlike retractile bodies. Ovary transversely oval, pretesticular. Vitelline follicles welldeveloped, lateral, between ovary and posterior extremity. Excretory bladder Y-shaped; excretory pore terminal. Second intermediate host. Cichlasoma urophthalmus (Cichlidae). Site of infection. Fins. Distribution. Campeche ( El Vapor). References from Mexico. Vidal-MartõÂnez et al. ( 2000); present data. Specimens deposited. CHCM-30. Remarks. The metacercaria found in ®ns (?) closely resembles those of A. (L .) mcintoshi as described above in all but one morphological features. The only diŒerence is in spination of the oral sucker: A. (L .) mcintoshi possesses two complete rows of circumoral spines whereas the present metacercaria has only one circle, i.e. its oral sucker is armed with only 20 spines instead of 38±42 in A. (L .) mcintoshi. Both taxa also diŒer in the site of location (®ns versus mesentery) and the second intermediate host (Cichlidae versus Poecillidae). Therefore, the specimen studied is provisionally identi®ed as Ascocotyle (Phagicola) sp. until new material is available. Centrocestus formosanus (Nishigori, 1924) (®gure 9AÐC ) Metacercaria Morphology . The most detailed description of metacercariae from Mexico was provided by Arizmendi (1992: 5±6; ®gure 3). Second intermediate hosts. Scholz and Salgado-Maldonad o (2000) reported 39 ®sh species of the following families: Atherinidae, Characidae, Cichlidae, Cyprinidae, Eleotridae, Gobiidae, Goodeidae, Ictaluridae, Mugilidae and Poeciliidae. The eleotrids such as Gobiomorus dormitor LaceÂpeÁde and G. maculatus (GuÈnther) and mugilids such as Agonostomus monticola (Bancroft in Grith and Smith) were the most susceptible hosts, harbouring up to 6000 metacercariae (Scholz and Salgado-Maldonado , 2000 Ðtable 2). Site of infection. Gills. Distribution. Scholz and Salgado-Maldonad o (2000) listed localities in 10 Mexican states (Colima, Guanajuato, Hidalgo, Jalisco, MichoacaÂn, Morelos, San Luis PotosõÂ, Tabasco, Tamaulipas, Veracruz) where C. formosanus metacercariae were found. Recent ®ndings from RõÂo GrandeÐGuelatao (State of Oaxaca) , RõÂo Atoyac and Santa MarõÂa Tecomavaca (Puebla), and Ciudad ObregoÂn (Sonora) extend the distribution of C. formosanus to 13 Mexican states. References from Mexico. Arizmendi (1992); Amaya-Huerta and Almeyda-Artigas (1994 ); Salgado-Maldonad o et al. (1995 ); VeÂlez-HernaÂndez et al. (1998 ); Scholz and Salgado-Maldonad o (2000), present study. Specimens deposited. CNHE 3708, IPCAS D-271. Adult Morphology . Experimentally recovered adults were described by Arizmendi (1992: 6±8; ®gure 4) and Salgado-Maldonad o et al. (1995). Because of some discrepancies between biometrical data of these authors, basic measurements of six hot formalin-®xed specimens are provided: body ¯ask-shaped, 370±460 long and 190±240 wide. Oral sucker 40±47 long and 47±57 wide, armed with a total of 32 circumoral 1757 Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae Fig. 9. (A±C ) Centrocestus formosanus. Metacercariae from the gills of Poecilia mexicana, RõÂo La Palma, Veracruz (A) and Xiphophorus sp., RõÂo Las MaÂquinas, Veracruz (B, C ). (D) Heterophyidae gen. sp. ( 5 Haplorchoides sp. of Scholz and VargasVaÂzquez, 1998). Metacercaria from the gills of Cichlasoma meeki, RõÂo Hondo, Quintana Roo. (A, D) excysted metacercaria, ventral view; (B, C ) encysted metacercaria. Note position of metacercarial cyst close to the cartilage (ca; bv, blood vessel ) of gill ®laments. spines arranged in two complete circles of 16 spines each. Anterior spines 10±14 long and 3±5 wide; posterior spines 10±12 long and 3 wide. Prepharynx 12±20 long; pharynx 37±42 long and 27±35 wide. Ventral sucker 42±55 long and 47±55 wide. Sucker ratio 150.92±1.17. Testes 52±72 long and 60±120 wide. Ovary 45±67 long and 60±112 wide. Seminal receptacle 42±57 long and 45±67 wide. Eggs 32Ô2 (27±35; n 526) long and 17Ô2 ( 15±22) wide. DeWnitive hosts. Butorides striatus (Linnaeus) (natural ), chicks and mice (experimental ). Site of infection. Intestine. Distribution. Hidalgo ( Tezontepec de Aldama). References from Mexico. Arizmendi ( 1992); Amaya-Huerta (1995Ðunpublished MSc thesis); Salgado-Maldonad o et al. (1995 ); Scholz and Salgado-Maldonad o (2000 ). Specimens deposited. BMNH 2000.6.1.10, CHCM-245, CNHE 3709, IPCAS D-419, USNPC 88539. Comments. Centrocestus formosanus was described from Taiwan (then Formosa) Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1758 T. Scholz et al. and it was imported to Mexico most likely in 1979 (LoÂpez-JimeÂnez, 1987). It has spread rapidly and is now one of the most abundant ®sh parasites in several regions (see Scholz and Salgado-Maldonado , 2000 for review). The thiarid snail of Asian origin, Melanoides tuberculata (MuÈller), serves as the ®rst intermediate host in Mexico (Arizmendi, 1992; Salgado-Maldonad o et al., 1995; Scholz and SalgadoMaldonado, 2000). *Euhaplorchis californiensis Martin, 1950 Metacercaria Morphology . No data are available. Second intermediate host. Fundulus grandissimus (Cyprinodontidae). Site of infection. Brain. Distribution. YucataÂn (CheleÂm). References from Mexico. Present study. Specimens deposited. None. Comments. During a study on the parasites of ®sh from the CheleÂm lagoon near Progreso, YucataÂn, carried out in January 1994, heterophyid metacercariae were found in the brain of four of 15 Fundulus grandissimus (mean intensity 9 metacercariae; range 5±16 specimens). Metacercariae ®tted in their morphology, in particular the presence of a conspicuous, pyriform gonotyl armed with anteriorly directed sclerites and the site of infection, into the diagnosis of the species Euhaplorchis californiensis described by Martin (1950a) from the brain of Fundulus parvipinnis in California. In November and December 1999, 37 F. grandissimus from the same locality were examined but no metacercariae were found. Since no specimens found in January 1994 were preserved, no description, measurements or illustrations based on Mexican material are provided in this paper. Fundulus grandissimus represents a new second intermediate host of the trematode that is reported from Mexico for the ®rst time. Martin (1950a) described the life cycle of this trematode, reporting the prosobranch snail Cerithidea californica, harbouring rediae and oculate, parapleurolopho cercous cercariae, to serve as the ®rst intermediate, and chicks and Californian gull (Larus californicus Lawrence) as experimental de®nitive hosts, respectively. Galactosomu m puni Yamaguti, 1941 (®gure 5E, F ) Adult Morphology . Bravo-Hollis (1966: 125±127; ®gures 1±3) described adult specimens. DeWnitive host. Larus occidentalis Audubon. Site of infection. Intestine. Distribution. Baja California ( Isla Rasa). References from Mexico. Bravo-Hollis (1966 ). Specimens deposited. CNHE 804. Comments. Galactosomum puni is a widely distributed parasite of ®sh-eating birds, above all of gulls (Laridae) and pelecans (Pelecanidae), reported from Japan, European part of the ex-USSR, USA, Puerto Rico, Panama and Colombia ( Hutton, 1964; Yamaguti, 1971; Pearson, 1973; Rietschel and Werding, 1978). In Florida, Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1759 other species of Galactosomum, namely G. cochleariforme ( Rudolphi, 1819), G. spinetum (Braun, 1901) and Galactosomum sp., were found in ®sh-eating birds and metacercariae of G. spinetum in the ®sh Hyporhamphu s unifasciatus ( Ranzani ) ( Hutton, 1964 ). *Haplorchis pumilio (Looss, 1896) (®gure 10) Metacercaria Morphology. (Morphology based on ®ve metacercariae from Gobiomorus maculatus and one metacercaria from Dormitator latifrons.) Cyst small, oval. Body elongate, 337±600 long and 113±184 wide, entirely covered with scale-like tegumental spines with rounded base and almost straight distal end. Remnants of eye-spots Fig. 10. Haplorchis pumilio. Metacercariae from the musculature of gill apparatus of Dormitator latifrons (A, E ) and Gobiomorus maculatus, Marismas de Chalacatepec, Jalisco (D, F ), and adults from mouse experimentally infected with ®ns of Cichlasoma managuense, El Espino, Tabasco (B) and gills of Cichlasoma salvini, RõÂo Puyacatengo, Tabasco (C ), 6 days post infection. (A) Total view of excysted metacercaria; (B, C ) total views of adults, dorsally (B) and laterally (C ); (D±F ) ventral sucker, ventrally (D, E ) and dorsally (F ); longitudinal axis of the body indicated by arrow. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1760 T. Scholz et al. dispersed between pharynx and ventral sucker. Oral sucker large, spherical, subterminal, 50±62 long and 54±67 wide, without spines. Prepharynx 5±57 long; pharynx spherical, 32±42 long and 25±30 wide; oesophagus long. Intestinal caeca wide, reaching to testis, containing discoidal corpuscles (bodies). Ventral sucker reduced, feebly muscular, forming part of ventrogenital complex, slightly postequatorial, 39±40 long and 37±52 wide. Sucker ratio 15 0.55±0.80. Ventral sucker armed with 28±31 concave bar-like sclerites with pointed ends, forming incomplete circle interrupted dorsally; anterolateral lobes with sclerites with fused bases; mid-dorsal lobe armed with seven to nine simple spines. Mouth of ventrogenital sac slit-like, perpendicular to body axis. Testis single, widely oval, postacetabular , 50±75 long and 62±92 wide. Ovary spherical, situated between ventral sucker and testis. Excretory bladder sacciform, voluminous, ®lled with small, dark granules. Excretory pore terminal. Second intermediate hosts. Cichlasoma helleri, C. managuense, C. salvini, Petenia splendida (Cichlidae); Dormitator latifrons, Gobiomorus maculatus ( Eleotridae). Site of infection. Musculature of gill arches, head and ®ns. Distribution. Jalisco ( Marismas de Chalacatepec); Tabasco ( El Espino, RõÂo Puyacatengo, YumkaÂ). References from Mexico. Present study. Specimens deposited. CNHE 3934, IPCAS D-279, USNPC 90186. Adult Morphology. (Morphology based on three hot formalin-®xed specimens from experimentally infected mouse; six DPI.) Body elongate, slightly tapering towards anterior extremity, 350±520 long and 180±210 wide, covered with serrate, scale-like tegumental spines. Oral sucker subterminal, 40±52 long and 35±57 wide; without circumoral spines. Prepharynx 7±22 long; pharynx oval to spherical, 32±40 long and 32±35 wide; oesophagus longer than prepharynx. Intestinal caeca long, reaching to testis. Ventral sucker feebly developed, recessed, slightly postequatorial, 37±52 long and 40±52 wide; sucker opening small, slightly anterolateral to sucker midline. Sucker ratio 150.74±1.30. Anteroventral margin of ventral sucker armed with incomplete circlet of 30±36 small bar-like sclerites with concave base and pointed lateral end; two groups of sclerites with fused bases on anterolateral lobes and a group of small simple spines on mid-dorsal lobe. Testis single, anterior to posterior extremity, 60±80 long and 67±105 wide. Seminal vesicle posterolateral to lateral to ventral sucker, 70 long and 40 wide. Ventrogenital sac formed; gonotyl absent. Mouth of ventrogenital sac large, slit-like. Ovary dextral, nearly spherical, anterodextral to testis, 30±50 long and 57±68 wide. Seminal receptacle voluminous, dorsal to ovary, 26±47 long and 32±42 wide. Uterus sinuous; uterine loops anteriorly reaching to ventral sucker, posteriorly near to posterior extremity. Vitelline follicles in postovarian region. Eggs operculate, 31Ô1 (29±32; n 515) long and 19Ô1 (17±20) wide. DeWnitive host. Chicks (experimental ). Site of infection. Intestine. Distribution. Not known. References from Mexico. Present study. Deposition of specimens. CNHE 3730, IPCAS D-256, USNPC 90187. Comments. Specimens from Mexico, both metacercariae and adults, correspond in all diagnostic features such as the armature of the ventrogenital complex, to H. pumilio (see Pearson, 1964). This trematode was originally described from Egypt Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1761 and it has been found in many ®sh-eating birds and mammals in North Africa, Asia and Australia (Pearson, 1964). In South-East Asia, H. pumilio belongs to the `small intestinal ¯ukes’, i.e. trematodes causing human ®sh-borne trematodose s ( Velasquez, 1982). The present ®ndings represent the ®rst record of this parasite from America. It was probably introduced to Mexico with the thiarid snail Melanoides tuberculata similarly to Centrocestus formosanus. Scholz et al. (2000) found cercariae of H. pumilio in M. tuberculata collected in the Cuitzmala River situated very near from the locality where metacercariae of H. pumilio occurred. Heterophyidae gen. sp. (Haplorchoides sp. of Scholz and Vargas-VaÂzquez, 1998 ) (®gure 9D) Metacercaria Morphology. (Morphology based on six ¯attened specimens from Cichlasoma meeki.) Cyst large, oval, thin-walled. Metacercaria elongate, tapering to both ends, 1273 ±1964 long and 280±343 wide, entirely covered with simple, long ( length 9±13) and slender (width 2) tegumental spines. Two pairs of eye-spots at prepharyngea l level. Oral sucker small, subterminal, spherical, 48±77 long and 54±83 wide. Ventral sucker spherical, postequatorial, 84±122 long and 99±122 wide, with opening armed with ®ne simple spines, 2 long, arranged in two to three irregular circles. Sucker ratio 151.50±2.06. Prepharynx variable in length, 176±462 long; pharynx large, heart-shaped, 80±98 long and 67±83 wide; oesophagus shorter than prepharynx. Intestinal caeca narrow and very long, reaching to posterior extremity. Single testis large, oval, intercaecal, anterior to excretory bladder, 186±212 long and 109±134 wide. Primordium of ovary oval, between ventral sucker and testis. Primordia of cirrus sac slightly curved, posterolateral to ventral sucker. Excretory bladder small, sacciform, ®lled with numerous dark granules. Excretory pore terminal. Second intermediate hosts. Strongylura timucu ( Walbaum) (Belonidae); Centropomus undecimalis (Bloch) (Centropomidae) ; Cichlasoma aureum, C. meeki (Cichlidae); Sphaeroides testudineus (Linnaeus) ( Tetraodontidae) . Site of infection. Gills, ®ns, muscles. Distribution. Campeche (La CaletaÐCiudad del Carmen); Quintana Roo ( Ramonal, RõÂo Hondo); YucataÂn (CelestuÂn). References from Mexico. Scholz and Vargas-VaÂzquez ( 1998); Vidal-MartõÂnez et al. (2000 ); present study. Specimens deposited. CHCM-360, IPCAS D-385. Comments. Metacercariae markedly diŒer from those of other trematodes in possessing an elongate body covered with very long, slender tegumental spines, a small oral sucker, much smaller than the acetabulum, a very long prepharynx, a heart-shaped pharynx and a single testis. In these features, the metacercariae best ®t into the diagnosis of the genus Haplorchoides Chen, 1949 as de®ned by Yamaguti (1971 ). However, they diŒer from all species of Haplorchoides in having a welldeveloped (not reduced ) ventral sucker lacking any sclerotized structures such as sclerites or spines, typical of Haplorchoides (see Yamaguti, 1971). Generic appurtenance of these metacercariae remains unclear and adult worms are necessary to assess their taxonomic position within the Heterophyidae. 1762 T. Scholz et al. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 *Phocitremoides ovale Martin, 1950 (®gure 11) Metacercaria Morphology . (Morphology based on 16 live metacercariae from Fundulus grandissimus.) Cyst almost spherical, thin-walled, 138±165 long and 128±163 wide. Excysted metacercaria elongate, 301±383 long and 138±163 wide, covered with conspicuous scale-like tegumental spines, pectinate in anterior third of body and decreasing in size posteriorly. Eye-spot remnants scattered between pharynx and acetabulum, sometimes present even in postacetabula r region. Numerous cells with granular Fig. 11. Phocitremoides ovale. Metacercariae from scales of Fundulus grandissimus, CheleÂm lagoon, YucataÂn (A, B, G) and adults from chicks experimentally infected with scales of F. grandissimus, 2 and 4 days post infection (C±F, H ). (A, D) Total view of excysted metacercaria and adult, respectively; ventrally; (B) encysted metacercaria; (C) detail of gland cells around oral sucker; (E, H ) acetabular region with terminal genitalia, dorsal (E ) and ventral (H ) views; (F ) egg; (G) intestinal caeca and acetabular region, ventrally; note granulation of cells of the intestinal wall. (A±C, E, G, H ) Free-hand illustrations based on observations of live specimens; not to scale. Abbreviations: ovs, opening (mouth) of ventral sucker; ts, tegumental spines; for other abbreviations see ®gure 2. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1763 content lateral to oesophagus and intestinal caeca. Oral sucker spherical to widely oval, 48±58 long and 48±68 wide. Prepharynx very short; pharynx strongly muscular, 25±32 long and 24±30 wide; oesophagus longer than prepharynx. Intestinal caeca long and wide, reaching to anterior arms of excretory bladder, ®lled with discoidal corpuscles; intestinal wall in posterior part with granular content (®gure 11G). Ventral sucker spherical, slightly postequatorial, embedded in parenchyma, 46±50 long and 48±52 wide. Sucker ratio 150.81±1.00. Testis single, large, near posterior extremity. Ventrogenital sac formed, thick-walled, anterior to ventral sucker. Ovary anterodextral to testis. Excretory bladder V-shaped, with short arms, reaching to anterior half of testis, containing numerous dark granules. Flame cell pattern not determined but cells apparently in pairs, with ®rst pair posterolateral to oral sucker and one pair posterolateral to acetabulum. Second intermediate hosts. Floridichthys polyommus, Fundulus grandissimus, F. persimilis (Cyprinodontidae). Site of infection. Scales (internal side). Distribution. YucataÂn (CheleÂm Lagoon). References from Mexico. Present study. Specimens deposited. None. Adult Morphology. (Morphology based on eight hot formalin-®xed specimens from chicks infected with metacercariae from scales of Fundulus grandissimus, 4 days post infection; measurements of seven ¯attened specimens in parentheses.) Body small, pyriform, 320±370 (390±580) long and 170±250 ( 192±230) wide, covered with scalelike tegumental spines. Pectinate spines with four to six teeth covering ventral surface except for periacetabular zone, decreasing in size and less dense posteriorly. Dorsal side covered with spines up to anterior margin of testis. Remnants of eye-spots scattered throughout body between pharynx and posterior extremity. Oral sucker widely oval, 45±50 (52±70) long and 47±52 ( 49±75) wide. Sucker surrounded by numerous elongate cells with granular contents; four small gland cells present near base of oral sucker (®gure 11C ). Prepharynx 12±22 (7±60) long; pharynx strongly muscular, 17±22 (22±30) long and 17±22 (17±27) wide; oesophagus longer than prepharynx. Intestinal caeca thick-walled, narrow and long, reaching posteriorly to excretory bladder. Ventral sucker spherical, slightly postequatorial, 39±40 ( 44±59) long and 40±47 (42±52) wide, recessed in parenchyma, with small opening situated slightly dextral to median line of body, separated from mouth of ventrogenital sac. Tegument at level of posterior margin of ventral sucker covered with semilunar circle of narrow, simple spines arranged in two to three irregular rows. Sucker ratio 150.81±0.95 (150.64±0.84). Testis single, 47±63 ( 80±105) long and 52±72 (90±92) wide, in posterior third of body. Seminal vesicle postero- to laterodorsal to ventral sucker, voluminous, bipartite, with feebly separated chambers often overlapping one another. Ventrogenital sac well-developed, thick-walled, opening by slit-like mouth, anterosinistral to ventral sucker; gonotyl absent. Ovary just anterior to testis, slightly shifted dextral to median line of body, 32±42 (36±50) long and 45±65 (52±80) wide. Seminal receptacle spherical, anterolateral to testis (32±42 long and 32±42 wide). Vitelline follicles small, laterodorsal to ovary and testis, anteriorly reaching to posterior margin of acetabulum, posteriorly not overlapping testis. Uterus tubular; uterine loops ®lling most space between caecal bifurcation and posterior extremity. Eggs operculate, 25.0Ô1.5 (range 23±28; n 536) ( 20±28) long and 15.1Ô1.3 (range Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1764 T. Scholz et al. 14±17.5) (10±16) wide. Excretory bladder V-shaped with short arms, not reaching to pretesticular level, containing numerous dark granules. DeWnitive hosts. Chick, duck (experimental ). Site of infection. Intestine. Distribution. Not known. References from Mexico. Present study. Specimens deposited. BMNH 2000.6.1.11, CHCM-351, CNHE 3936, IPCAS D-395, USNPC 90196. Comments. Metacercariae were found exclusively in scales of three species of cyprinodonti d ®sh that represent new second intermediate hosts. The parasite was infrequent in Floridichthys polyommus but very common in both species of Fundulus. The morphology of the metacercariae corresponds to that of metacercariae of Phocitremoides ovale found in experimentally infected Atherinopsis californiensis Girard and Fundulus parvipinnis ( Martin, 1950b). Adults from experimental hosts were almost identical in their morphology and measurements, including the egg size, to those described by Martin (1950b) as Phocitremoides ovale. There was only a slight diŒerence in the shape of the body that was reported to be oval to pyriform by Martin (1950b: ®gure 1) whereas the trematodes from Mexico were elongate and pyriform, thus not corresponding to the speci®c name `ovale’. However, this diŒerence may be related to diŒerent ®xation of worms. Martin (1950b: ®gure 1) illustrated the mouth of the ventral sucker to be common with that of the ventrogenital sac. In fact, both openings are distinctly separated one from another as observed both in living and ®xed metacercariae and adults (®gure 11D, G ). Natural de®nitive hosts of P. ovale are not known and adults were obtained only from experimentally infected hosts (Martin, 1950b; Yoshino, 1972) in California. Oculopleurolophocercou s cercariae of P. ovale were found in Cerithidea californica (Prosobranchia) . The present data expand the range of distribution of P. ovale to the Atlantic coast of Mexico, from which it is reported for the ®rst time. *Pygidiopsis pindoramensis ( Travassos, 1929) (®gure 12) Metacercaria Morphology. (Morphology based on 12 metacercariae from Poecilia catemaconis, three from Xiphophorus helleri Heckel and one from Poecilia mexicana; measurements of ¯attened specimens ®xed with GAP in parentheses.) Cyst widely oval to almost spherical, (230±340) long and (230±310) wide, with thick external wall and thin, hyaline internal wall. Body pyriform, 280±370 (500±650) long and 150±280 (250±310) wide, covered with scale-like tegumental spines, with convex base and serrate distal end, overlapping one another. Spines covering almost completely ventral side except for small area around subterminal excretory pore; dorsally spines reaching only to testicular level. Remnants of eye-spots at pharyngeal level. Oral sucker spherical, without posterior appendage, 30±38 ( 42±58) long and 30±40 (42±57) wide, with one complete row of 16 ®ne circumoral spines and four additional spines on dorsal side. Prepharynx 36±67 (32±97) long; pharynx oval, 26±32 (38±47) long and 20±28 (37±45) wide; oesophagus longer than prepharynx. Intestinal caeca long and narrow, surrounding ventral sucker, slightly curved medially in posterior part, reaching to ovarian level and containing discoidal corpuscles. Ventral sucker 1765 Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae Fig. 12. Pygidiopsis pindoramensis. Metacercariae from the gill arches of Poecilia catemaconis, Catemaco Lake, Veracruz (A±C ), fatty body of Poecilia mexicana, Balzapote stream, Los Tuxtlas, Veracruz (D, E), and mesentery of Xiphophorus helleri., Catemaco Lake, Veracruz (F ). (A, C ) Total view of excysted metacercaria, dorsally (ts, tegumental spines); (B, D) encysted metacercaria (thick-walled external cyst wall not ®gured in B); ( E) anterior end, ventral view; note 16 spines in one complete row and four additional spines on the dorsal side (dotted); (F ) terminal genitalia, dorsally. (C ) Free-hand schematic drawing. spherical, slightly postequatorial, 32±37 (48±71) long and 37±43 (60±65) wide. Sucker ratio 151.00±1.28 (151.09±1.42). Testes symmetrical, close to posterior extremity, 23±35 (34±74) long and 24±45 (44±75) wide. Ventrogenital sac formed, anterosinistral to acetabulum, containing widely oval gonotyl with 13±17 narrow refractile bodies. Mouth of ventrogenital sac irregularly oval, opening anteroventral to cavity of ventral sucker. Ovary almost spherical, posterior to acetabulum, 18±25 (25±52) long and 26±31 (33±55) wide. Primordia of vitelline follicles forming two bands lateral to testes between ventral sucker and posterior extremity. Flame cell pattern 2 [(21 2)1 (21 2)] 516. Excretory bladder Y-shaped with short and wide arms or X-shaped with feebly developed posterior lobes, ®lled with numerous small, dark granules. Excretory pore subterminal. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1766 T. Scholz et al. Second intermediate hosts. Poecilia catemaconis, P. mexicana, Xiphophorus helleri. (Poeciliidae). Site of infection. Gill arches, heart, fatty body. Distribution. Veracruz (Balzapote, Catemaco). References from Mexico. Present study. Specimens deposited. CHCM-355, CNHE 3933, IPCAS D-444. Comments. Metacercariae of P. pindoramensi s were previously found in the mesentery and ovary of cyprinodonti d ®sh Phalloceros caudimaculatu s (Hensel ) and Cnesterodon decemmaculatus from Argentina (Ostrowski de NuÂnÄez, 1974 ). Ostrowski de NuÂnÄez (1976) reported cercariae of P. pindoramensi s from the prosobranch snail Littoridina piscium d’Orbigny from Argentina. The same author (Ostrowski de NuÂnÄez, 1996) described another species of Pygidiopsis, for which the name P. australis was proposed. This species cannot be distinguished in metacercarial or adult stage from P. pindoramensis and diŒers only in cercarial morphology (the arrangement of penetration glands and the absence of pigment granules). Since the actual distribution of P. australis is not known and P. pindoramensi s has been reported from North and South America (see Ostrowski de NuÂnÄez, 1996), the specimens from Mexico are tentatively considered to belong to the latter species. Discussion In the present review, 20 species of Heterophyidae are reported from Mexico, either as metacercariae encysted in ®sh or as adults in the intestine of ®sh-eating birds and mammals. Seven of these species, Ascocotyle (Ascocotyle) gemina, A. (Leighia) mcintoshi, A. (Phagicola) ampullacea, Euhaplorchis californiensis, Haplorchis pumilio, Phocitremoides ovale and Pygidiopsis pindoramensi s, are reported from this country for the ®rst time. In the checklist of the helminth parasites of continental water ®sh of Mexico, PereÂz-Ponce de LeoÂn et al. (1996 ) listed metacercariae of only 10 species of heterophyid trematodes. In addition, most of them were not identi®ed to species level or were misidenti®ed. Because of the number of incorrectly or not speci®cally identi®ed species of the Heterophyidae from Mexico and confusions in the taxonomy of this group in the literature, a brief survey of these records is added with remarks on individual species reported. Phagicola angrense of diŒerent authors (see below), nec Travassos, 1916 As demonstrate d by Scholz et al. (1997a) , metacercariae from the internal organs of cichlid ®sh from southeastern Mexico had been misidenti®ed as Phagicola angrense ( Travassos, 1916 ) ( 5Ascocotyle (Phagicola) angrense Travassos, 1916) by SalgadoMaldonado and Aguirre-Macedo ( 1991), JimeÂnez-GarcõÂa (1993), and AguirreMacedo and GarcõÂa-MaganÄa (1994 ). Ascocotyle (P.) angrense is characterized by the presence of 181 2 circumoral spines (versus 161 4 in A. (P.) nana) and its metacercariae encyst exclusively in the gills of the atheriniform ®sh Phalloceros caudimaculatus (Ostrowski de NuÂnÄez, 1993). To date, A. (P.) angrense has not been found in Mexico and its distribution may be limited to South America. Ascocotyle (A.) sp. 1 of Scholz et al. (1995 ) Scholz et al. (1997a) identi®ed these metacercariae found in the intestinal wall of Poecilia velifera ( Poeciliidae) from Sahkaba cenote, YucataÂn as A. (L .) megalocephala. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1767 Ascocotyle (Phagicola) sp. 2 of Scholz et al. ( 1995 ) Metacercariae encysted in the internal organs of numerous cichlids and other freshwater ®sh were conspeci®c with A. (P.) nana (see Scholz et al., 1997a). Ascocotyle (Phagicola) sp. 3 of Scholz et al. ( 1995 ) Metacercariae from the gills of Cichlasoma meeki were described by Scholz et al. (1997b ) as a new species for which the name Ascocotyle (L .) nunezae was proposed. Phagicola sp. of Iruegas et al. ( 1983 ) In an unpublished contribution at a national congress, metacercariae were reported from the operculum and musculature of Cichlasoma cyanoguttatu m (Baird and Girard ) (Cichlidae) and Poecilia mexicana ( Poeciliidae) from RõÂo PesquerõÂa in Nuevo LeoÂn. Although no description or illustration of the metacercariae were provided, it can be assumed that the metacercariae belonged to the species Ascocotyle (Phagicola) nana that commonly occurs in Mexico as well as in southeastern USA ( Font et al., 1984b; Scholz et al., 1997a). Heterophyidae gen. sp. of Scholz et al. (1995 ) This metacercaria apparently belonged to a species of the Ascocotyle-complex because of the presence of a complete row of circumoral spines, most probably to A. (L .) nunezae. However, this species possesses additional spines on the dorsal spines and its metacercariae encyst exclusively in the gills. Despite a relatively high number of taxa reported from Mexico, further heterophyid trematodes may still be found in Mexico. There are several species such as Ascocotyle (Ascocotyle) pachycystis Schroeder and Leigh, 1965; A. (A.) puertoricensis Price, 1932; A. (A.) sexidigita Miller and Harkema, 1962; A. (P.) mollienisicola Sogandares-Berna l and Bridgman, 1960; or species of Galactosomum, that occur in the neighbouring countries, especially in the southern part of the USA ( Florida, Louisiana, Mississippi) (Price, 1932, 1935; Sogandares-Berna l and Bridgman, 1960; Miller and Harkema, 1962; Hutton, 1964; Schroeder and Leigh, 1965; Yoshino, 1972 ). As demonstrate d by Ostrowski de NuÂnÄez (1993), Scholz et al. (1997a) , Scholz (1999 ) and in this study, the number of circumoral spines may be very constant and species-speci®c. However, this is valid mainly for those taxa that possess a relatively low number of spines such as A. (P.) angrense (181 2), A. (P.) diminuta (161 2), A. (P.) longa (16), A. (P.) macrostoma (18) or A. (A.) tenuicollis ( 161 16). In contrast, the number of spines may be subjected to some intraspeci®c variation in the species that have higher number of spines such as A. (L .) megalocephala (36±40 in one row), A. (L .) mcintoshi (19±21 in one row) and A. (L .) nunezae (25±261 6±10). Species of the Ascocotyle-complex represent the dominant group of heterophyids in Mexico but their subgeneric classi®cation is unsatisfactorily resolved and a new arrangement should be proposed. However, such an arrangement requires a phylogenetic analysis of the group which will be possible only after more complete data on the morphology of individual species and their developmental stages, including cercariae, are available. Because of the existence of sibling species among heterophyids in North and South America ( Font et al., 1984a; Ostrowski de NuÂnÄez, 1992, 1996 ), life-cycle studies should be carried out and more thorough descriptions of Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 1768 T. Scholz et al. the morphology of metacercariae and adults of many taxa should be provided. Current classi®cation, largely based on the topography of female genital organs (vitelline follicles, uterine loops) and the number of rows of circumoral spines, is apparently arti®cial and several species present intermediate characters which do not allow their placement within well-de®ned taxonomic entities. Acknowledgements The authors are indebted to Guillermina CabanÄas-Caranza, Rafael BaÂez-VaÂle, Griselda Moreno-Navarette , Rogelio Aguilar-Aguilar, Petra SaÂnchez-Nava ( Instituto de BiologõÂa, Universidad Nacional AutoÂnoma de MeÂxico, MeÂxico); Juan Manuel Caspeta-Mandujan o (Centro de Investigaciones BioloÂgicas, Universidad AutoÂnoma del Estado de Morelos); Dr Victor Manuel Vidal-MartõÂnez, Isabel JimeÂnez-GarcõÂa, Clara Vivas-RodrõÂguez, David GonzaÂlez-SolõÂs, Edgar MendozaFranco and Gregory Arjona-Torres (CINVESTAV-IPN, MeÂrida, Mexico) for help in sampling and examining ®sh. Thanks are also due to Drs J. Ralph Lichtenfels and Patricia A. Pilitt, US National Parasite Collection, Beltsville, MD, USA; and Rafael Lamothe-Argumedo and Luis GarcõÂa-Prieto, Institute of Biology, UNAM, Mexico City, Mexico, for lending types of species of Ascocotyle and vouchers of Ascocotyle `leighi’ and Galactosomum puni, respectively. This study was partly supported by scienti®c projects of the ComisioÂn Nacional para el Conocimiento y Uso de la Biodiversidad (CONABIO), Mexico, project No. M-135 (M. L. Aguirre-Macedo and V. M. Vidal-MartõÂnez) and Consejo Nacional de Ciencia y TecnologõÂa (CONACyT ), Mexico, project No. 211085-5-3008N , and the Catherine McArthur Foundation. A stay of one of the authors ( T. S.) in Mexico was supported by CONACyT MeÂxico (catedra patrimonial ) and CINVESTAV-IPN MeÂrida, and partly by the Institute of Parasitology, CÏeske BudeÏjovice and the Grant Agency of the Czech Republic (project No. 206/98/0591). His short stays in the ®eld stations Chamela (Jalisco) and Los Tuxtlas ( Veracruz) were supported by the Institute of Biology, UNAM, MeÂxico. A stay of M. L. A.-M. in the Czech Republic in August 1999 was supported by the Ministery of Foreign AŒaires of Mexico (SecretarõÂa de Relaciones Exteriores). References ~ a, L., 1994, Metacercarias de cõÂclidos nativos Aguirre-Macedo, M. L. and GarciÁa-Magan del Sureste de MeÂxico; taxonomõÂa y claves para su reconocimiento, Universidad y Ciencia, 11, 5±35. Amaya-Huerta, D., 1995, Algunos aspectos de la transmisioÂn y dispersioÂn de Centrocestus formosanus (Trematoda: Centrocestinae) en el Estado de Morelos, MeÂxico. MSc thesis, Faculty of Biology, National Autonomous University of Mexico ( UNAM ), Mexico, 119 pp. Amaya-Huerta, D. and Almeyda-Artigas, J., 1994, Con®rmation of Centrocestus formosanus (Nishigori, 1924) Price, 1932 (Trematoda: Heterophyidae) in Mexico, Research and Reviews in Parasitology, 54, 99±103. Arizmendi, M. A., 1992, DescripcioÂn de algunas etapas larvarias y de la fase adulta de Centrocestus formosanus de Tezontepec de Aldama, Hidalgo, Anales del Instituto de BiologõÂa, Universidad AutoÂnoma de MeÂxico, Serie ZoologõÂa, 63, 1±11. Bravo-Hollis, M., 1966, Reporte de Galactosomum puni Yamaguti, 1941, tremaÂtodo con nueva localidad y nuevo hospedador, Anales del Instituto de BiologõÂa, Universidad AutoÂnoma de MeÂxico, Serie ZoologõÂa, 37, 125±128. Burton, P. R., 1956, Morphology of Ascocotyle leighi, n. sp. (Heterophyidae), an avian trematode with metacercaria restricted to the conus arteriosus of the ®sh, Mollienesia latipinna Le Sueur, Journal of Parasitology, 42, 540±543. Downloaded By: [EBSCOHost EJS Content Distribution] At: 13:09 24 March 2008 Trematodes of the family Heterophyidae 1769 Burton, P. 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